The present invention concerns a method and an apparatus for estimating a maximally transmissible drive torque in a motor vehicle.
A method and an apparatus of this kind are described in an example of a drive slip control system from German Published Patent Application No. 44 30 180, in which the maximally transferable drive torque of the drive unit of the motor vehicle is estimated on the basis of the estimated coefficient of friction between the drive wheels of the vehicle and the road surface. The drive torque generated by the drive unit is then held at that maximally transferable drive torque. A satisfactory estimate of the maximally transferable drive torque is made available with this procedure, but the estimate of the coefficient of friction can be subject to a few uncertainties.
It is therefore the object of the present invention to describe actions with which the determination of the maximally transmissible drive torque can be optimized.
The publication entitled xe2x80x9cFDRxe2x80x94Die Fahrdynamikregelung von Boschxe2x80x9d (FDRxe2x80x94the Bosch Vehicle Dynamics Control System) written by Anton van Zanten, Rainer Erhardt, and Georg Pfaff, Automobiltechnische Zeitschrift (ATZ) 1996, pp. 674-689, describes a drive slip controller, subordinate to the vehicle dynamics controller, in which a so-called propeller shaft speed controller is used. The latter regulates the average wheel speed of the drive wheels to a predefined setpoint.
The approach according to the present invention makes available a reliable, optimized estimate of the maximally transmissible drive torque (at the wheel level).
It is particularly advantageous that the estimate is relatively easy and accurate: the result of the estimate is not impaired by gradients or slopes of the road surfaces, changes in the mass of the vehicle, or vehicle accelerations.
It is particularly advantageous that the estimate of the maximally transmissible drive torque is not adapted under certain conditions, for example, when the estimate would not lead to a satisfactory result. Operating situations of this kind are, for example, traveling through curves, an operating situation in which aquaplaning occurs, during a gear-change operation, and/or in the event of an active vehicle dynamics controller intervention and/or drive slip controller intervention.
It is particularly advantageous that the moment of inertia of the drive train can also be taken into account in estimating the maximally transmissible drive torque, thus making the estimate even more accurate.